1. Field of the Invention
This invention relates to a circuit arrangement for starting a trackbound electric propulsion vehicle having a synchronous linear motor without iron. More particularly, the motor has a stator, designed as a traveling-field winding, installed along the line, and an exciter, designed as a translator, arranged on the propulsion vehicle. The traveling-field winding is supplied with voltage and frequency from a stationary, controlled static converter in response to an associated control device having a computing circuit for determining the travel velocity and the relative position of the exciter with respect to the traveling-field winding from the phase currents and voltages at the feed point.
2. Description of the Prior Art
A circuit arrangement of the general type just described is discussed in German Pat. No. 23 41 761. In it, the current in the traveling-field winding determines the magnitude of the propulsion force developed in a propulsion vehicle having a synchronous linear motor. The frequency of the current determines the velocity. An appropriately designed control sees to it that the synchronous linear motor is operated, as far as possible, at the optimum operating point. The control device generates control voltages for the control unit of the converter as setting signals. For such a control, knowledge of the operating condition of the linear motor and, in particular, its pole position is required. Pole position, or vehicle position angle, is the relative position of the exciter with respect to the traveling field winding. The vehicle position angle can be determined from electrical measurements made at the point at which the converter feeds into the traveling field winding. This known, indirect method of measurement is based on the consideration that all information important for the control can be determined from the main field voltage induced in the traveling-field winding by motion of the exciter in translation. In particular, the speed of the vehicle can be determined from the frequency of the main field voltage and the pole position, from its phase angle. This measuring method does not work when a propulsion vehicle is standing still, since no main field voltage is induced in the traveling-field winding by the then stationary exciter.
It is an object of the present invention to provide a circuit arrangement which makes it possible to start up a vehicle propelled by a synchronous linear motor without iron in which the motor does not fall out of step and in which undesirable hunting does not occur.